CD4 and esophageal squamous cell carcinoma: For HLA-DRB1, Hu et al. proved that HLA-DRB1B1 methylation changes can promote the occurrence and progression of ESCC [28]; Yu et al. reported the association between brain DNA methylation of HLA-DRB1B5 and pathological diagnosis of Alzheimer disease [29]; Graves et al. discovered that methylation at the HLA-DRB1B1 locus in CD4+ T cells are associated with multiple sclerosis [30].